The present invention relates to a process for enzymatic oxidation of soluble as well as insoluble oligo- or polysaccharides such as starch and cellulose wherein the oligo- or polysaccharide is oxidized introducing carbonyl groups and/or carboxylate groups giving products with improved functional properties.
Oxidation of polysaccharides by various chemicals are known in the art:
Oxidation of cellulose, for example, causes changes in the structure and crystallinity of the resulting molecule, which affects its chemical and physical properties. Varma and Chavan [Varma, A. J., and Chavan, V. B. (1995), Polymer Degradation and Stability, 49, pp 245-250] found a proportionality between the decrease in degree of crystallinity and increase in degree of oxidation. Further, Varma and Chavan from cellulose created sodium 2,3-dicarboxy cellulose by oxidizing cellulose to 2,3-dialdehyde cellulose by periodate oxidation followed by oxidation of the 2,3-di-aldehyde cellulose to 2,3-di-carboxy cellulose by sodium chlorite. The 98% sodium 2,3-dicarboxy cellulose was found to be water soluble.
Further, oxidized polyglucosides have interesting properties as calcium sequestrants and are useful as tripolyphosphate substitutes in detergent formulation [Santacesaria, E., Trulli, F., Brussani, G. F., Gelosa, D., and Di Serio, M. (1994), Carbohydrate Polymers, 23, pp 35-46].
Further, various kinds of polysaccharides, in particular starch, are of utmost importance as a sizing agent in the textile industry, in addition to application as a processing aid in printing and finishing. However, the properties of the native starch is not always optimal compared to the properties required for the particular application. One of the problems of native starch is the very large molecular size, the insolubility, the instability of viscous solutions under varying temperature, and its susceptibility to microbial degradation. Consequently, chemical modification of starches has become an important tool to overcome the problems and create starches having altered characteristics compared to the native starch. Common treatments involve acid treatment, oxidation, etherification, esterification, grafting, and preparation of poly (vinyl)-starch composites [Abdel-Hafiz, S. A. (1997), Polymer Degradation and Stability, 55, pp 9-16].
In addition, Hebeish et al. [Hebeish, A., El-Kashouti, M. A., Abdel-Thalouth, I., Haggag, K., and El-Halwagi, A. (1994), Cellulose Chemistry and Technology, 28, pp 409-418] have shown, that the degree of substitution when Carboxy Methyl Cellulose (CMC) is produced depends on the degree of oxidation of the cellulose base-material, and various qualities of CMC can thus be produced using cellulose with varying degrees of oxidation.
There is thus an increasing interest in and need for methods capable of introducing oxidative changes of various kinds in oligo- and polysaccharides.
The present invention relates to a process for oxidation of a hydroxy group of C1 and/or C2 and/or C3 and/or C4 and/or C5 and/or C6 of a sugar monomer of an oligo- or a polysaccharide comprising contacting, in an aqueous medium, the oligo- or the polysaccharide with a phenol oxidizing enzyme, together with a hydrogen peroxide source when the phenol oxidizing enzyme is a peroxidase, and an enhancing agent, whereby an oligo- or a polysaccharide with altered characteristics compared to the native oligo- or polysaccharide is created.